Stainless steel having excellent brazeability

Abstract

A stainless steel exhibiting an excellent brazeability includes in mass %: C: from 0.001% to 0.1%; Si: from more than 1.5% to 4.0%; Mn: from 0.05% to 4.0%; Cr: from 10.5% to 30%; Ni: 35% or less; N: from 0.001% to 0.4%; one or both of Ti: 0.002% to 0.030% and Al: 0.002% to 0.10%; and a balance being Fe and inevitable impurities, in which an Si content, a Ti content and an Al content satisfy Formula 1, and an oxide film with a composition satisfying Formula 2 is formed on a surface of the stainless steel, Si m /(Ti m +Al m )≥40  Formula 1 1.2×Si m Fe m ≤Si f /Fe f ≤5×Si m /Fe m   Formula 2 in Formula 1 and Formula 2, a suffix “f” expresses the oxide film in a unit of atom %, and a suffix “m” expresses a base material in a unit of mass %.

The invention claimed is: 
     
       1. A stainless steel, comprising, in mass %:
 C: from 0.001% to 0.1%; 
 Si: from 2.11% to 4.0%; 
 Mn: from 0.05% to 4.0%; 
 Cr: from 10.5% to 30%; 
 Ni: 35% or less; 
 N: from 0.001% to 0.4%; 
 Ti: 0.002% to 0.008%; and 
 Al: 0.002% to 0.10%; and 
 a balance being Fe and inevitable impurities, wherein 
 an Si content, a Ti content and an Al content satisfy Formula 1, and 
 an oxide film with a composition satisfying Formula 2 is formed on a surface of the stainless steel,
   Si m /(Ti m +Al m )≥40  Formula 1
 
   1.2×Si m /Fe m ≤Si f /Fe f ≤5×Si m /Fe m   Formula 2
 
 
 
       where: in Formula 1 and Formula 2, an element with a suffix “f” expresses a content of the element in the oxide film, the content being indicated by a unit of atom %, and an element with a suffix “m” expresses a content of the element in the stainless steel that is a base material, the content being indicated by a unit of mass %. 
     
     
       2. The stainless steel according to  claim 1 , further comprising, in mass %: at least one of:
 a first group that is at least one of Sn: from 0.001% to 0.5%, Co: 0.01% to 0.5%, Bi: 0.001% to 0.01%, and B: 0.0002% to 0.005%; 
 a second group that is at least one of Mo: 0.3% to 8%, W: 0.3% to 4%, V: 0.05% to 0.5%, Nb: 0.01% to 1%, Cu: 0.1% to 6%, Sb: 0.001% to 0.5%, Zr: 0.001% to 0.3%, Ga: 0.0001% to 0.01%, and Ta: 0.0001% to 0.01%; and 
 a third group that is at least one of Ca: 0.0002% to 0.005%, Mg: 0.0002% to 0.005%, and REM: 0.005% to 0.1%. 
 
     
     
       3. The stainless steel according to  claim 2 , wherein at least one of the Si content, the Ti content and the Al content in mass % satisfy respective ranges below:
 Si: from 2.11% to 3.4%; 
 Ti: from 0.003% to 0.008%; and 
 Al: from 0.003% to 0.03%. 
 
     
     
       4. The stainless steel according to  claim 3 , used as a joined member for brazing with an Ni braze or a Cu braze. 
     
     
       5. The stainless steel according to  claim 4 , used for a heat exchanger. 
     
     
       6. The stainless steel according to  claim 3 , used for a heat exchanger. 
     
     
       7. The stainless steel according to  claim 2 , used as a joined member for brazing with an Ni braze or a Cu braze. 
     
     
       8. The stainless steel according to  claim 7 , used for a heat exchanger. 
     
     
       9. The stainless steel according to  claim 2 , used for a heat exchanger. 
     
     
       10. The stainless steel according to  claim 1 , wherein at least one of the Si content, the Ti content and the Al content in mass % satisfy respective ranges below:
 Si: from 2.11% to 3.4%; 
 Ti: from 0.003% to 0.008%; and 
 Al: from 0.003% to 0.03%. 
 
     
     
       11. The stainless steel according to  claim 3 , used as a joined member for brazing with an Ni braze or a Cu braze. 
     
     
       12. The stainless steel according to  claim 11 , used for a heat exchanger. 
     
     
       13. The stainless steel according to  claim 10 , used for a heat exchanger. 
     
     
       14. The stainless steel according to  claim 1 , used as a joined member for brazing with an Ni braze or a Cu braze. 
     
     
       15. The stainless steel according to  claim 14 , used for a heat exchanger. 
     
     
       16. The stainless steel according to  claim 1 , used for a heat exchanger. 
     
     
       17. The stainless steel according to  claim 1 , used for an automobile component that is an exhaust gas recirculation cooler, an exhaust heat recovery equipment, or a fuel delivery component. 
     
     
       18. The stainless steel according to  claim 1 , used for a CO 2  refrigerant heat pump-type hot water supplier, a secondary heat exchanger of a latent heat recovery-type hot-water supplier, or a plate type heat exchanger.